Electrical resistance device



1932- E. N. LIGHTFOOT ELECTRICAL RESISTANCE DEVICE Filed Feb. 19, 1930 2 Sheets-Sheet las 23 25 i Nov. 29, 1932- E. N. LIGHTFOOT ELECTRICAL RESISTANCE DEVICE 2 sheets-sheet 2 Filed Feb. 19, 1950 Patented Nov. 29, 1932 S AT -s EDWIN n. memoor, or wauwnrosa. WISCONSIN, AssIsNoR r01 CUTLER-HAMER, -nvc.,:.o n arrnwnnxnn. w rsoonsm, A con-roaurroiv or DELAWARE PATENTEOFFICE ansrsriincn nnvfcn j .Th isiinventionrelates" to improvements in electrical' res'istance devices, and "more particularly to, devices wherein resistances of ribbon or strip type are employed. Anyob ject' offthe'invention is to provide improved-supporting means for resistors of Another o Je'ct is to generally improve and simplify the details of construction of the parts of resistance devices of the aforementioned character.

' Another object is to provide such a device possibility of warping'or sagging thereof irrespective of themanner of mountingof the device as awhole. p

T Another object is to minimize the number.

" of diiferent types and cost of the parts re-' quired to produce a device of the aforementioned character.

Gther objects and advantages of the invention will hereinafter appear.

' The accompanying drawings-illustrate an embodiment of the invention which will now be described, it being understood that the embodiment illustrated issusceptible of mod-.

ification within .the scope of the appended claims.

In the drawings, Figure 1 is a side elevation of a resistance device constructed in accordance with my invention.

Fig. 2 is an end elevation of the device illustrated in Fig. 1, and showing terminal elements and a bus wire providing for series connection of the two resistance ribbons.

Fig. 3 is a View similar to Fig. 2, but partly diagrammatic; and showing a type of terminal element providing for parallel connection of the resistance ribbons.

4 is an enlarged fragmentary sectional view on the line i of Fig. 1, showing the manner of assembling and insulating the resistor supporting elements with respect to the 4 the resistance strip or ribbon as to avoidany Application fi1ed' Fe bruary 19, 1930. Serial No..429,'s'75.

frame rod, and showingthe means for spac ing and insulating said elements with'respect to each-other." T f Fig. 5' is a fragmentary perspective'view of one of the one-piece resistance ribbons, showing the'flatwise reflexedor zigzag formation effected prior to assembly thereof with respect to the supportingelements. Fig. 6 is a plan view of one of the punched sheet metal supporting elements,''all" of which are of identical form'and size.

Fig. -7 is a side viewpf one form of terminal device. f p v Figs. 8and 9 are "perspective views of the two forms of punchedand stamped sheet metal plates required to produce'the terminal deviceofFig.7.' 1 f A F g.'10 is a side view of one of the terminal devices .which may be employed to connect p the resistance ribbons in parallel relation to achpther."

F ig.-11 is a perspective view of one of the punched and stamped sheet metal. plates shown in Fig. 10,the other plates shown in gig. 10 being identical with that shown in Fig. 12 is a perspective view of the terminal wire clamping .member to be employed with the terminal device of Figs. 10 and 11.

Fig. 13 is a plan view of one of the punched metal spacing elements or washers shown in section in Fig. 4, and

Fig. 14: is a plan view of one of the insulating w'ashers shown in Fig.4.

Referring to the drawings, the numerals 20 and 21 designate'a pair of straight cylindrical metal rods which are preferably of equal length, and each having relatively long threaded portions at opposite ends thereof. Slidable onto and rather closely fitting each rod is a tube or covering 22 (Fig. 4) of a tough and substantially unbreakable insulating material suchas laminated mica. The tube 2-2 surrounding rod 20 is preferably of somewhat greater length than the corresponding tube surrounding rod 21, for a purpose to be described.

The resistor supporting elements to be strung upon the rods 20 and 21 are-all of the form shown in Fig. 6 and consist of fiat punched sheet metal )lates 23 each having a relatively large circu lar perforation 24 adjacent to one end thereof, and a pairof relatively wide alined notches 25 and 26 adjacent to the other endthereof. Located in aline midwaybetween the notches, 2,5, 2and spaced apart distanee slightly jigreat'ei'i than. the width of the latter are a pair of perforations 27 and 28. As will appear, only one of the distances'fromthe. ends of'the rod. Thereupon'.a relativ'ely thickivasher 27. of insulatingImaterial preferably laminated mica, is strung upon rod 2Qand o'izer oneend of the insulating tube 22,- a metal washer 28' haying aperforation'of less diameter than that of tii e 22 beinglpbsitioned in abutting relation to washer 2'(', '..and ainut 29 being threaded onto rod20 to back up or prevent endwise movement of said. washer 28. If desired a split'or. lock. washer .30 may be. interposed betweennut29and'fwasher 28.

Thereafter the" other elements: may he strung. upon,rod,2 (l from, theopposite side of \vaslieri'gii Thus .a metal .washer 32 having a perforation -to..acconunodate the diameter of tube 22'is brought into abutting relation to, washer Thereafter a pairof spacing washers 53ers strungupon the tube 22, then aninsulating. washer 34,-pi'eferably of laminated. mica, then; one of the supporting elements 23, then another insulating washer 34:, and so on until the desired number of supporting elements 23 have been placed in position upon-the rod. Then the end washers .32., 27, 28 and 30 and nut 29 are brought to position.- Prior to tightening the last mentioned nut 29 and either during or after stringing of the supporting elements upon the rod said elements are arranged so that they extend alternately in diametrically opposite directions. 'VVhen such arrangement of elements 23 has been effected either or both of the nuts 29 may be tightened until all of the partsstrung upon rod20 are socurely held against movement relatively to the rod and alsoagainst movement with respect to each other.

The required number of resistor supporting elements 23 are strung'upon the rod 21 and the same are insulated from red 21 and spaced and insulated from each other in exactly the same manner as described in conneetion with the assembly of parts on rod 20. It will be noted, however, that in an arrangement of the character illustrated in Figs. 1

ightened so that the porting elements 23 on opposite sides of the latter may be temporarily positioned at predetermined upwardly divergent angles with respect to each other.

Thereupon the opposite threaded ends of rods 20 and 21 may be inserted into correspondingly shaped perforations in a pair of rectangular end plates 35 and 36 toprovide for support of said rods in spaced parallel relation to each other. Nuts on rod 20 may be utilized to insure proper spacing of the end plates 35 and 36,nuts 37 and splitwashcrs 38 being employed to rigidly sec are the end plates and rods to each other. As shown, additional lock nuts 39 are required upon the rod 21 to insure proper a ine" out of said end plates. It will be understood, of course, that the end plates might be more Widely spaced from each other, in which event additional nuts corresponding with those indicated at 39 would also be required upon the rod 20.

'End plates 35 and 36 are provided with integral flanges. extending in parallel relation from the two longer edges thereof, as shown at 40 and H -said end plates being also preferably provided with end flanges i2 and d3, andthe adjacent edges of the flanges 10 to 43 may he tack welded or otherwise rigidly securedto each other. The flanges 4-0 and 41 are each provided with notches 4 1 to provide for securing a plurality of units to each. other when the same are in stacked or banked relation as by means of suitable clamping bolts, not shownl in practice, however, when a. number of complete units are stacked or banked with respect to each other it preferred to interpose between the suitable spacing members, which may convenient-lv consist of elements ident cal with or six ilar to the flanged. end plates and 36.

As shown each unit preferably includes two one-piece strips or ribbons composed of a suitable metal alloy resistance. such for instance as the usual nickel-chromium or copper-nickel alloys. Each strip is bent or refiexed fiatwise at a multiplicity of points to provide a resistor of form, as shown at 45 in Fig. 5. When a strip or ribbon of relatively thin steer. is employed I preferably provide a plurality of Lc .tively short reinicucingbeads or corrugations at each localized point of ham ing thereof, a provide one or more longitudi reinforcing beads d? between t bends and spaced endwise with respect to he latter,--. ,Ontthe other-hand,;:if the -strip iis formed of sufficiently thick, istoel'r'i'certain or all of saidreinforcing beads-may beomitted. With: thelaforedescribed supporting;ele. ments 2?) assembled upon the ,mspective rods 2 n 21 .ai diwi h t e lat er secur d to; th

end. plates and 36in such manner; that the" i st n erthevupvardly; a d; ppo t m nts ca rie by od bei g t pp o dr v n e her indiv d al yrsai mly nt nterlwk ng. en twith theoppo er (ivend e mi t Wh nee f; th re s s asth sbe t semble up The terminal,

essentiallyapunchedandstampedsheet metal P at 58 h v n leg 49 i'and. tm o t wardly. frorn,one,.s1de; thereof and adapted for. interlocking. .engagement with. the. walls imrf r t bn 27la i 2 nian ne Ofthe snpp iiie elem i s -..l% e e8. sjp v d t :theeweniende'th ept with enieivy 'w re ti na ep stf r lem ingi ga e. ment 'iwith :the 1. resistor ribbon. at} .at one side;

ff? b'e' d a he e ena dfl eilp t nd bt p a e. 4 i c rr ed.- a show /m nd 52 i 1 t p o f r 'c mp ng a em thereof terminal 5 wires ,of, different difl mensions. i I Opposed to. 1 plate .48 I is .a punched stamped plate 53, the lower portionfit. of which is. oifsetoutwardly with respect to the upper portion 55 thereof, said plate .hav-

ing a partially.severedportion 56, pressed inwardly threfrom to interlock with the walls of the notch 2501-26 which supports the particular. bend ofthe resistor; A Y A bolt .57 .pene-;

tratcs registering openings 58 and 5 9 in plates 53 and/l8; and. av nut 60 is threaded upon theend of said. bolt to. draw saidplates into clamping engagement withthe resistor bend and the terminal wire and into interlocking engagement with the supporting element.

When it .is desired to provide clamping means for, a plurality of terminal wires of likedimensions a plate8 which is an exact duplicate ofplate 418, may be employed, the plate 53 being provided with notches 61, 62inthe .side edges thereofto, receive the projecting lugs on plate 48?, one vofwhichis shown at 49%.": A

Four of the terminal devices (two of which have the plate48 omitted) are shown at-- tached to the supporting elements at the ret eh ned ofl eeur lyi mp. Said e t- A p 4 disclosed of extremely simple and efiicient form and. as shown in Figs, 7, 8 and 9. each comprises BEST AVAILABLE CUP: 3

s'pective ends of :the two resistor ;ribbons,''a relatively heavy'buswire 63, preferably hav-Z ing ;a; heat resisting covering :of woven asbestos or ,thelike, being. shown as connecte ingthe iresistor ribbons in series relation to.

each other-,iandthe terminal devicesiatdiagoe na-lly opposite corners of the unit ibeingf ar? ranged for attachment .of the circuit or-lead' wires, not shown.- 1 W As will be'apparent, the

may be .attached to the supporting elements at the-rpoints' illustrated in- F igs.-- l and 42101. to. any other alternative or additional points on. the respective I resistors. This arrangement, provides for tapping off or wiring-theresistance unit-:in any desiredmanner, thus rendering 1 the: same .-of extremely [flexible- Htllltyp ,1 I7 ,L'l J If it is desired to electricallyconnect:the resistors inparallel relation to, eacl1 'ot l1er the combination .terminal devices illustrated in Fig. 3 and in detail in Figs. lOSand-glLare preferably employed. zThese\, termi i1 1-l devicesj' each comprise essentially a. punchedand stamped sheet metal plate be, having fiat poitions .65 and 66 offset with 'respectto. each other in parallel planes, 5 with a integral =angular connecting; portion 6.7. y 5 Plates 48? of the ident calform sl1ownat-48 inFigsa 7 and 8. are employed :for. cooperation ,with,

portions 65..and {66.whereby platefil and:

plate. 48? re g d y e dtee Pa r: supporting elements 23 and in clampingmela;

5 7Fand nuts. 50*, are tightened...

tion. 0 a pair of resistonbends when. the bolts i 9- Thejntermediate portion 67 of plate G i Qi s perforated 'to, accommodate a bolt. '68 3) said'bolt being also adapted to per g iate a wire terminal clamping element. 69, redraw thelattelr towar'd portion 67 when nutfitl tightened Element 69' may be formed cast'iron, and asshown in Fig. 12 the same is preferably prov-idedwith at least two sets (if substantially semi-circular wire-rece ving grooves 71 vand 72 of different d mensions, wherebywires of difierent sizes may beprop; erly clamped thereby. I

v The perforations 73 in plates 53and the perforations 74 in plate (i l are utilized for attachment of suitable metalv tags. ;(not shown),-which tags may be embossed or stamped to indicate the ohmic value or other characteristic of, the resistance unit as a Whole or at any part cular'point at which atapping. oft terminal is provided. In practice it is preferred to mount th complete units in superimposed relation to each other in the plane illustrated in Figs. 2 and 3 with-any desired degree of spacing therebetween. Effective ventilation -of; the

the arrangement provides for rapid and substantially unobstructed movement of air-i around and between the folds of the resistors blag.

with consequent rapid dissipation of heat and low temperature of the resistors. Also it will be apparent that the spacing of the resistor supporting elements may be readily varied as desired to thereby increase or decrease the space between the resistor folds. In somelcases close spacing is desira ble, as for starting duty. In other cases wide spacing is desirable, as for continuous duty and for assembly of the resistor units in large banks or stacks; Moreover, the novel manner of supporting the resistor elementsherein disclosed efi'ectivelyprovides for expansion and contraction of the latter without danger of distortion or displacement thereof with respect to the supporting members or the clamping terminal members of the device.

What I claim as new and by Letters-Patent is:

1. As an article of manufacture, an electrical resistance device comprising a onepiece metal strip resistor bent flatwise at a plurality of points to provide an element of zigzag form, supporting means for said ele-' ment comprising a pair of metal rods and a plurality of sets of one-piece flat punched sheet metal supports carried thereby, the individual supports of each set being insulated from said-rods and from each other, and said sets of supports being so arranged and maintained at such distance apart that the supports engage the resistor at or near itsrespective bends.

2; As an article'of manufacture, an electrical resistance device comprising a onepiece metal strip resistor bent fiatwise at a plurality of pointsto provide an element of zigzag form, supporting means for said element comprising two sets'of one-piece fiat punched sheet metal supports, each set of supports being mounted upon a metal rod,

desire to secure and means for insulatingthe individual sup-' ports in each set from each other and from their respective metal rods, the two sets of assembled supports being so arranged and maintained at such distance apart that the supports engage the resistor at or near its respective bends.

3. As an article of manufacture, an electrical resistance device comprising a metal strip resistor bent fiatwise at a plurality of points to provide an element of zigzag form, supporting means for said element comprising two sets'of supports formed of punched sheet metal, each set of supports being mounted upon a metal rod, means for spacing and insulating the individual supports in each set from each other and including means for insulating the same from their respective metal rods, each of said supports having a notched portion within which the respective bends of the resistor element are adapted to seat, and the two sets of assembled supports being so arranged and maintained at such distance apart that the resistor bends are-re tained within said notches. 4. As an article of manufacture, an electrical resistance device comprising a metal strip resistor bent-fiatwise at=a plurality of points to provide an element'of zigzag form, supporting means for said element compris ing two sets of supports formed of-punched sheet metal, each set of supports being r'nounted upon a metal rod,me'ansfor spacing and insulating the individual supports in-each set from each other and including means for in sulating the same fromtheir're'spective metal rods, each of said supports having a-notched portion within which the respective bends of the resistor'element are adapted to seat, and the two sets of assembled supportsbeing'so arranged and maintained at such distance apart that the resistor-bends are retained within said notches, said resistorfelement' ha-i ing one or more longitudinally extending-re inforcing beads formed therein between -the respective bends thereof to prevent sagging of said element under-relatively hightemperature conditions. i

5. As an article'of n'ianufacture, a"resistance unit comprising a pair of metal rods located in spaced parallel relation to each other, a plurality of punched'sheet metal support; ing members strung upon the'respective' rods,- means for spacim and insulating said sup-' porting members Irom' each other -an' d from the respective rods, the groups of supporting members-upon the respective rods having portions projecting-from thelatter in parallelplanes and the supporting members iii the respective groups being positioned in stage gered relation to each other, and a one-pieceribbon resistor bent fiatwise to zigzag form,

each bend of said resistor being adapted for interlocking engagement with one of said supporting'members.

6. In a device of the character described, 111' combination, a metal rod having threads at the opposite ends thereof, a multiplicity of resistor supporting elements strung upon said rod, spacing members interposed between the respective supporting elements, each of'said supporting elements and said spacing mer'n'' bers consisting of a fiat sheet metalpunching,

insulating members for electrically separabin said sheet metalsu )ortin elements from said rod and from each other, the resistor spective ends thereof to clamp said support-- ing elements in fixed position on said rod.

7. As an article of manufacture, a supportmg element for a resistor of the ribbon type,

said element consisting'of a flat sheet metal punching havinga relatively large opening adjacent to one end thereof to provide for stringing thereof upon a suitable support, said element having a relatively wide and relatively deep notch adjacent to the other end to provide a shouldered support for the reflexed portion of a resistor, and a pair of relatively smaller openings located on opposite sides of said notch, for the purpose set forth.

8. As an article'of manufacture, a supporting element for a resistor of the ribbon type, said element consisting of a fiat sheet metal punching having a relatively large circular opening adjacent to one end thereof to pro vide for stringing thereof upon a supporting rod, said element having a pair of relatively wide notches in alinement with each other adjacent to the other. end thereof, and a pair ofrelatively smaller openings located in a line intermediate said notches and spaced apart a distance slightly greater than the width of the latter.

99A resistance unit comprising a pair of metal frods located inspaced parallel relation to each other, a tube of insulating material surrounding each of said rods, a plurality of one-piece flat punched sheet metal supportingmembers strung upon the respective rods and separated therefrom by said insulating tubes, the supporting members on each rod being spaced and insulated from each other and said members being located upon the respective rods in staggered relation to each other, a one-piece ribbon resistor bent fiatwise to zigzag form, each bend of said resistor being adapted for engagement with one of said supporting members, certain of said supporting members being movable in the planes thereof respectively into interlocking relation with said resistor, and adjustable securing means on the respective rods for jointly holding said members in relatively fixed position.

10. A resistance unit comprisin end plates and a pair of metal rods rigi ly secured thereto in spaced parallel relation, each of said rods having a relatively long tube of insulating material strung thereupon, a multiplicity of one-piece flat punched sheet metal supporting members strung upon the respective insulating tubes and insulated from each other, the supporting members of the two groups being symmetrically offset with respect to each other, a one-piece resistor strip bent fiatwise to zigzag form and having each bend thereof in cooperative engagement with an edge portion of one of said supporting members, and a terminal member adapted for positive interlocking engagement with any one of said supporting members, said terminal member also having clamping engagement with the adjacent bend of said resistor.

11. In. combination, a metal rod and a resistor supporting member carried thereby but insulated therefrom, said supporting member consisting of a flat punched sheet metal piece having a relatively deep notch formed in an edge thereof to receive and retain the bent portion of a resistorof the ribbon type while permitting free expansion and contraction of said resistor, said supporting member having perforations on opposite sides of said notch, and a clamping terminaldevice comprising a pair of punched sheet metal plates-respectively provided with portions adapted'for interlocking engagement with theTWallS of said perforations and said notch when said plates are drawn toward each other by their common fastening means, each of said plates also having portions adapted for clamping engagement with said bent portion of the resistor, to thereby provide agood mechanical support for said terminal device and to provide a good electrical connection betweenthe latter and the resistor.

12. In combination, a metal rod and a resistor supporting member carried thereby but insulated therefrom, said supporting member consisting of a flat punched sheet metal piece having a relatively deep notch formed in an edge thereof toreceive and retain the bent portion of a resistor of the ribbontype, said supporting member having perforations on opposite sides of said notch and a clamping terminal device comprising a pair of punched and stamped sheet metal plates of identical form and a third punched and stamped sheet metal plate to be'interposed between said first mentioned plates, one of said first mentioned plates having projecting portions for interlocking engagement with the walls of said perforations and said third plate having a project-ing portion for interlocking engagement with the walls of said notch, said third plate having notches in the opposite side edges thereof with the walls of which notches the projecting portions of the other of said first mentioned plates are adapted'to engage, said third plate and one of said first mentioned plates also having portions adapted for clamping engagement with said bent portion of theresistor, and common means for holding all of said plates in assembled and adjustable relation to each other.

13. In combination, a metal rod and a resistor supporting member carried thereby but insulated therefrom, said supporting member consisting of a flat punched sheet metal piece having a relatively deep notch formed in an edge thereof to receive and retain the bent portion of a resistor of the ribbon type, said supporting member having perforations on opposite sides of said notch and a clamping terminal device comprising a pair of punched and stamped sheet metal plates of identical form and a third punched and stamped sheet metal plate to be interposed between said first mentioned plates, one of said first mentioned plates having projecting portions for interend plates in spaced parallel relation to each other, a multiplicity of punched sheet metal supporting elements strung upon the respective rods, punched sheet metal spacing members also strung upon said rods and interposed between the respective supporting elements, insulation separating said supporting elements from the respective rods and from said spacing members, common means on each rod for securing said supporting elements in relatively adjusted positions, the supporting elements on each rod extending alternately in opposite directions from the latter and said rods being adjusted with respect to said end plates to provide an offset or staggered relationship of the two groups of supporting elements on each of the respective sides of said pair of rods, and one-piece flexible resistor ribbons supported respectively by each two groups of supporting elements, each of said ribbons being bent fiatwise into zigzag form and said supporting elements having relatively deep notches to receive the respective bends of said ribbons While permitting freedom of expansion and contraction of the latter, wiring terminal means comprising a plurality of punched metal plates adapted for positive interlocking engagement with any one of said supporting elements when said plates are drawn toward each other by their common fastening means, said plates also having portions adapted for clamping engagement with the corresponding bends of the resistor ribbons.

18. In an electrical resistance unit, in combination, a pair of punched sheet metal end plates, said end plates having integral flanges extending outwardly at right angles from at least two edges thereof to provide for assembly of said units in groups, a pair of rods extending between and rigidly secured to said end plates in spaced parallel relation to each other, a multiplicity of punched sheet metal supporting elements strung upon the respective rods, punched sheet metal spacing members also strung upon said rods and interposed between the respective supporting elements, insulation separating said supporting elements from the respective rods and from said spacing members, common means on each rod for securing said supporting elements in relatively adjusted positions, the supporting elements on each rod extending alternately in opposite directions from the latter and said rods being adjusted with respect to said end plates to provide an offset or staggered relationship of the two groups of supporting elements on each of the respective sides of said pair of rods, one-piece flexible resistor ribbons to be supported respectively by each two groups of supporting elements, each of said ribbons being bent fiatwise into zigzag form and said supporting elements having relatively deep notches to receive and retain the respective bends of said ribbons, wiring tervals to provide an element of zigzag form,

of supporting means for said resistor comprising a pair of metal rods and a plurality of sets of one-piece fiat punched sheet metal supports carried thereby, the individual supports of each set being insulated from said H rods and from each other, the formed resistor being freely insertable over said sets of supports for engagement of the alternate bends of the former with one set of the latter, and means providing for movement of the other set of supports into engagement with the other bends of said resistor to secure the latter'in position.

20. In a resistance unit, the combination with a strip resistor bent flatwise at intervals to provide an element of zigzag form, of supporting means for said resistor comprising a pair of metal rods and a plurality of sets of one-piece flat punched sheet metal supports carried thereby, the individual supports of each set being insulated from said rods and from each other, the formed resistor being freely insertable over said sets of supports for engagement of the alternate bends of the former with one set of the latter, and means providing for movement of the other set of supports into engagement with the other bends of said resistor to secure the latter in position, the supports of each set having notches to be engaged by the respective bends to insure proper support of the resistor under conditions of expansion and contraction of the latter when in use.

21. In a resistance unit, the combination with a strip resistor bent flatwise at equally spaced points to provide an element of zigzag form, of a pair of metal rods each having a set of notched supports extending laterally therefrom, said formed resistor being movable bodily onto one of said sets of supports, means providing for movement of the other set of supports into interlocking engagement with the respective bends of the resistor to properly support the latter, and means common to each set of supports for clamping the same in relatively fixed relation.

In witness whereof, I have hereunto subscribed my name.

EDWIN N. LIGI-ITFOOT. 

